Why does my iPhone ask for a screen time password when I’ve never set up one?

I literally set up screen time on my iPhone this morning and went through all the app limits, “this is my iPhone” etc. However I have never set up a screen time password on that device before and when I tried to change the app limits “enter screen time password” popped up on my screen and I have no idea what the password is. I have other Apple devices (with the same Apple ID) with screen time set up I think, so could this be part of the problem? Thanks